After taking Cathy Johnson's Sketchbook Skool Seeing klass, I picked up a couple of Cathy Johnson's books from the library: Creating Nature in Watercolor an Artist's Guide and Watercolor Pencil Magic. I loved both of these books so much, I purchased Cathy Johnson's Artist's Sketchbook - Exercises and Techniques for Sketching on the Spot from Amazon.
I can't recommend these books more. Cathy is so inspirational and shows that there are an infinite subjects to sketch! Here are some of my recent sketches inspired by Cathy's teachings.